Heat oil in saucepan over medium heat. Add onion, and cook 10 minutes, or until starting to brown, stirring often. Stir in garlic, cumin, coriander, ginger, and cinnamon, and saute 30 seconds. Add tomatoes, chickpeas, and 1/4 cup water; simmer 10 minutes.
Meanwhile, toast couscous in small saucepan over medium heat 5 minutes, or until fragrant. Add 1 3/4 cups water, and bring to a boil. Remove from heat, cover, and let stand 5 minutes.
Stir dates and lemon juice into tagine, and season with salt and pepper, if desired. Serve over couscous, sprinkled with cilantro.